We just spent a week in HK and our trip to Lantau was a definite highlight.
We started our day with an excellent dim sum brunch at the moderately-priced 3rd floor Maxim restaurant in City Hall (5 Edinburgh Place) with its bustling atmosphere and great view of the HK waterfront. Don't confuse it with the more formal dining room on the second floor.
Then we walked over to the Outlying Islands Ferry Pier No. 6 (to the west of the Star Ferry) and took the 50-minute trip to Mui Wo on Lantau Island.
From Mui Wo we took Bus 2 on a scenic, winding climb up to Ngong Ping where the Giant Buddha and Po Lin Monastery are located. It's a wonderful, serene atmosphere. After climbing the 259 steps (our daughter counted them) up to the world's tallest, seated, outdoor, bronze Buddha, we took in the monastery and enjoyed a vegetarian snack which is included in price of admission (HK$24).
There's an excellent sounding hike down from the Ngong Ping described in the indispensible Hong Kong Tourist Board publication "Hong Kong Walks". But on the day of our visit the weather was sketchy and we opted instead to take bus 21 to the fishing village of Tai O. This turned out to be an inspired choice.
Visiting Tai O is like looking in on old rural China -- at least it seemed that way to me. The village houses are rudimentary, built on stilts and made of tin. We walked from the busstop to the iron bridge and crossed to the main part of town, walking past tiny shops, simple restaurants and lots of stilt houses to Hau Wong Temple.
Many of the doors were open and we glimpsed the modest homes of the villagers.
Tai O is only a couple of hours from Hong Kong but it's a big step back in time. I would have loved to have eaten a meal in one of the restaurants on the main street, but we weren't sure of the bus and ferry schedules and didn't want to miss our connections.
We took bus 1 back to Mui Wo and then the ferry back to HK, but you could also choose bus 11 to Tung Chung where the airport MTR can whisk you back to the city.
All the transportation info you need is clearly posted in English as well as Chinese. Using the Octopus card to pay our ferry and bus fares saved a lot of hassle as buses don't give change.
If you're looking for a day away from the hustle and bustle of Hong Kong, Lantau Island is a perfect choice.